[Docs] Version warning about viewing old docs doesn't work for versions >= 10

[jorisvandenbossche]

Currently, if viewing older docs (eg https://arrow.apache.org/docs/9.0/python/index.html), you get a warning about that you are not viewing the latest docs. However, now that the newest "old" docs (those that are stored in a version/ subdirectory) is 10.0, that doesn't seem to work for this version (eg https://arrow.apache.org/docs/10.0/python/index.html doesn't show the warning)

My first guess is that it's caused by a bump in number of characters in the major version number (7, 8, 9 etc -> 10), and that this if check no longer works as expected because of that:

arrow/docs/source/_static/versionwarning.js

Lines 104 to 105 in 177a0d4

	} else if (versionPath.match(/^\d/)) {
	// older versions (with numbered version in the URL)

[AlenkaF]

I have created a PR to correct the current state of the documentation apache/arrow-site#312

Note from that PR:

Also, additional copying of the versionwarning.js file seems to happen with the release. Currently there are three versions of the same document:

• docs/_static/versionwarning.js
• docs/dev/_static/versionwarning.js
• docs/10.0/_static/versionwarning.js

Second and third should be redundant and are removed with this PR. I will create a separate issue on the apache/arrow repo to research and correct how the versionwarning.js file is being copied.

I plan to create a separate PR to correct the versionwarning.js file in the apache/arrow repo after the PR on apache/arrow-site is merged and the warnings are working well.

[AlenkaF]

The issue about multiple copies of versionwarning.js in apache/arrow-site: #34160